With increasing commercialization of 10G-PONs and increasing maturity of a next-generation PON technology, a high-speed optical module raises increasingly urgent requirements for a high responsivity (which may also be referred to as high flexibility), high-bandwidth photodetector. Although a high-speed PIN detector may have a very high speed and relatively low costs, responsivity of the high-speed PIN detector is also relatively low; therefore, it is difficult to meet a requirement of a high-speed PON network for flexibility and a power budget. An APD may have very high responsivity due to a multiplication effect, and therefore becomes a preferred high-speed optical module.
Currently, a 10 Gb/s APD is costly, and the APD has a relatively strong dark current, limiting flexibility of the APD.